Constructed solely for war, sayabito are fearsome human weapons who are tightly bonded to those who wield them. In the wake of a great war, fiery and impatient Rivia and her willowy, cautious partner Kuifa roam the land in search of sayabito who lost their wielders in the conflict, in order to register and protect these vulnerable sayabito before they wither away or are exploited. Though Rivia and Kuifa frequently exasperate each other with their clashing approaches, they share one common goal: to carve out a life in the peacetime for which they, and others like them, were never meant.
With the war over and no battlefields remaining, where do the sayabito belong? In order to manage these weapons, Kuifa and Rivia journey across the world to protect unregistered sayabito on behalf of the government organization, the Protettori. When rumor swirls around an aging horticulturist, the pair go knocking on his door. The girl who answers, however, is the spitting image of the man’s late daughter… Before long, Kuifa and Rivia learn that not all the sayabito they meet want to be saved, and some are even moved to take matters into their own hands.